Period of each state












1












$begingroup$


I am trying to determine the period of each state $ j = 0, 1, 2$ for this irreducible Markov Chain with transition probability matrix
$$P=begin{bmatrix}0&0&1\1&0&0\frac{1}{2}&frac{1}{2}&0end{bmatrix}$$



All states are of period $1$ because $0 rightarrow 2 rightarrow 0$ and $0 rightarrow 2 rightarrow 1 rightarrow 0$ have $gcd(2,3) =1$



Is this correct and is the proof sound?










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    $begingroup$
    Yes, the Markov Chain is aperiodic because of the two cycles you have identified whose lengths are relatively prime.
    $endgroup$
    – Fabio Somenzi
    Dec 8 '18 at 6:35
















1












$begingroup$


I am trying to determine the period of each state $ j = 0, 1, 2$ for this irreducible Markov Chain with transition probability matrix
$$P=begin{bmatrix}0&0&1\1&0&0\frac{1}{2}&frac{1}{2}&0end{bmatrix}$$



All states are of period $1$ because $0 rightarrow 2 rightarrow 0$ and $0 rightarrow 2 rightarrow 1 rightarrow 0$ have $gcd(2,3) =1$



Is this correct and is the proof sound?










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    Yes, the Markov Chain is aperiodic because of the two cycles you have identified whose lengths are relatively prime.
    $endgroup$
    – Fabio Somenzi
    Dec 8 '18 at 6:35














1












1








1





$begingroup$


I am trying to determine the period of each state $ j = 0, 1, 2$ for this irreducible Markov Chain with transition probability matrix
$$P=begin{bmatrix}0&0&1\1&0&0\frac{1}{2}&frac{1}{2}&0end{bmatrix}$$



All states are of period $1$ because $0 rightarrow 2 rightarrow 0$ and $0 rightarrow 2 rightarrow 1 rightarrow 0$ have $gcd(2,3) =1$



Is this correct and is the proof sound?










share|cite|improve this question









$endgroup$




I am trying to determine the period of each state $ j = 0, 1, 2$ for this irreducible Markov Chain with transition probability matrix
$$P=begin{bmatrix}0&0&1\1&0&0\frac{1}{2}&frac{1}{2}&0end{bmatrix}$$



All states are of period $1$ because $0 rightarrow 2 rightarrow 0$ and $0 rightarrow 2 rightarrow 1 rightarrow 0$ have $gcd(2,3) =1$



Is this correct and is the proof sound?







probability statistics stochastic-processes markov-chains markov-process






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asked Dec 8 '18 at 3:28









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  • 1




    $begingroup$
    Yes, the Markov Chain is aperiodic because of the two cycles you have identified whose lengths are relatively prime.
    $endgroup$
    – Fabio Somenzi
    Dec 8 '18 at 6:35














  • 1




    $begingroup$
    Yes, the Markov Chain is aperiodic because of the two cycles you have identified whose lengths are relatively prime.
    $endgroup$
    – Fabio Somenzi
    Dec 8 '18 at 6:35








1




1




$begingroup$
Yes, the Markov Chain is aperiodic because of the two cycles you have identified whose lengths are relatively prime.
$endgroup$
– Fabio Somenzi
Dec 8 '18 at 6:35




$begingroup$
Yes, the Markov Chain is aperiodic because of the two cycles you have identified whose lengths are relatively prime.
$endgroup$
– Fabio Somenzi
Dec 8 '18 at 6:35










1 Answer
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oldest

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$begingroup$

Comment: Here are some computations in R that I have sometimes
found convenient for use with ergodic Markov Chains having small finite
state spaces.
[If the matrix $mathbf{P}$ is based on empirical data, make sure each row of the
transition matrix sums exactly to $0.]$



Establish ergodicity. $mathbf{P}^8$ is a power of the transition matrix in the current Question that
has all positive elements, so the chain is ergodic.



P = matrix(c(0, 0, 1,
1, 0, 0,
.5,.5, 0), nrow=3, byrow=T)
P
[,1] [,2] [,3]
[1,] 0.0 0.0 1
[2,] 1.0 0.0 0
[3,] 0.5 0.5 0

P2 = P %*% P; P4 = P2 %*% P2; P8 = P4 %*% P4; P8
[,1] [,2] [,3]
[1,] 0.4375 0.1875 0.3750
[2,] 0.3750 0.2500 0.3750
[3,] 0.3750 0.1875 0.4375


Compute limiting distribution. The stationary vector $sigma$ with $sigmamathbf{P} = sigma$
is also the limiting distribution of the ergodic chain. For an
ergodic matrix, the left eigenvector with the largest modulus
is real and is proportional to the steady state vector.



eigen(t(P))$vectors     # transpose to get LEFT eigenvectors
[,1] [,2] [,3]
[1,] -0.6666667+0i -0.3535534+0.3535534i -0.3535534-0.3535534i
[2,] -0.3333333+0i -0.3535534-0.3535534i -0.3535534+0.3535534i
[3,] -0.6666667+0i 0.7071068+0.0000000i 0.7071068+0.0000000i

s = as.numeric(eigen(t(P))$vectors[,1]); s = s/sum(s); s
[1] 0.4 0.2 0.4 # first-listed vector has largest modulus

s %*% P # to verify stationarity
[,1] [,2] [,3]
[1,] 0.4 0.2 0.4


So $sigma = (.4, .2, .4)$ is the limiting distribution.



Perhaps there is more-elegant R code for this. If so, suggestions are
welcome.






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    $begingroup$

    Comment: Here are some computations in R that I have sometimes
    found convenient for use with ergodic Markov Chains having small finite
    state spaces.
    [If the matrix $mathbf{P}$ is based on empirical data, make sure each row of the
    transition matrix sums exactly to $0.]$



    Establish ergodicity. $mathbf{P}^8$ is a power of the transition matrix in the current Question that
    has all positive elements, so the chain is ergodic.



    P = matrix(c(0, 0, 1,
    1, 0, 0,
    .5,.5, 0), nrow=3, byrow=T)
    P
    [,1] [,2] [,3]
    [1,] 0.0 0.0 1
    [2,] 1.0 0.0 0
    [3,] 0.5 0.5 0

    P2 = P %*% P; P4 = P2 %*% P2; P8 = P4 %*% P4; P8
    [,1] [,2] [,3]
    [1,] 0.4375 0.1875 0.3750
    [2,] 0.3750 0.2500 0.3750
    [3,] 0.3750 0.1875 0.4375


    Compute limiting distribution. The stationary vector $sigma$ with $sigmamathbf{P} = sigma$
    is also the limiting distribution of the ergodic chain. For an
    ergodic matrix, the left eigenvector with the largest modulus
    is real and is proportional to the steady state vector.



    eigen(t(P))$vectors     # transpose to get LEFT eigenvectors
    [,1] [,2] [,3]
    [1,] -0.6666667+0i -0.3535534+0.3535534i -0.3535534-0.3535534i
    [2,] -0.3333333+0i -0.3535534-0.3535534i -0.3535534+0.3535534i
    [3,] -0.6666667+0i 0.7071068+0.0000000i 0.7071068+0.0000000i

    s = as.numeric(eigen(t(P))$vectors[,1]); s = s/sum(s); s
    [1] 0.4 0.2 0.4 # first-listed vector has largest modulus

    s %*% P # to verify stationarity
    [,1] [,2] [,3]
    [1,] 0.4 0.2 0.4


    So $sigma = (.4, .2, .4)$ is the limiting distribution.



    Perhaps there is more-elegant R code for this. If so, suggestions are
    welcome.






    share|cite|improve this answer











    $endgroup$


















      0












      $begingroup$

      Comment: Here are some computations in R that I have sometimes
      found convenient for use with ergodic Markov Chains having small finite
      state spaces.
      [If the matrix $mathbf{P}$ is based on empirical data, make sure each row of the
      transition matrix sums exactly to $0.]$



      Establish ergodicity. $mathbf{P}^8$ is a power of the transition matrix in the current Question that
      has all positive elements, so the chain is ergodic.



      P = matrix(c(0, 0, 1,
      1, 0, 0,
      .5,.5, 0), nrow=3, byrow=T)
      P
      [,1] [,2] [,3]
      [1,] 0.0 0.0 1
      [2,] 1.0 0.0 0
      [3,] 0.5 0.5 0

      P2 = P %*% P; P4 = P2 %*% P2; P8 = P4 %*% P4; P8
      [,1] [,2] [,3]
      [1,] 0.4375 0.1875 0.3750
      [2,] 0.3750 0.2500 0.3750
      [3,] 0.3750 0.1875 0.4375


      Compute limiting distribution. The stationary vector $sigma$ with $sigmamathbf{P} = sigma$
      is also the limiting distribution of the ergodic chain. For an
      ergodic matrix, the left eigenvector with the largest modulus
      is real and is proportional to the steady state vector.



      eigen(t(P))$vectors     # transpose to get LEFT eigenvectors
      [,1] [,2] [,3]
      [1,] -0.6666667+0i -0.3535534+0.3535534i -0.3535534-0.3535534i
      [2,] -0.3333333+0i -0.3535534-0.3535534i -0.3535534+0.3535534i
      [3,] -0.6666667+0i 0.7071068+0.0000000i 0.7071068+0.0000000i

      s = as.numeric(eigen(t(P))$vectors[,1]); s = s/sum(s); s
      [1] 0.4 0.2 0.4 # first-listed vector has largest modulus

      s %*% P # to verify stationarity
      [,1] [,2] [,3]
      [1,] 0.4 0.2 0.4


      So $sigma = (.4, .2, .4)$ is the limiting distribution.



      Perhaps there is more-elegant R code for this. If so, suggestions are
      welcome.






      share|cite|improve this answer











      $endgroup$
















        0












        0








        0





        $begingroup$

        Comment: Here are some computations in R that I have sometimes
        found convenient for use with ergodic Markov Chains having small finite
        state spaces.
        [If the matrix $mathbf{P}$ is based on empirical data, make sure each row of the
        transition matrix sums exactly to $0.]$



        Establish ergodicity. $mathbf{P}^8$ is a power of the transition matrix in the current Question that
        has all positive elements, so the chain is ergodic.



        P = matrix(c(0, 0, 1,
        1, 0, 0,
        .5,.5, 0), nrow=3, byrow=T)
        P
        [,1] [,2] [,3]
        [1,] 0.0 0.0 1
        [2,] 1.0 0.0 0
        [3,] 0.5 0.5 0

        P2 = P %*% P; P4 = P2 %*% P2; P8 = P4 %*% P4; P8
        [,1] [,2] [,3]
        [1,] 0.4375 0.1875 0.3750
        [2,] 0.3750 0.2500 0.3750
        [3,] 0.3750 0.1875 0.4375


        Compute limiting distribution. The stationary vector $sigma$ with $sigmamathbf{P} = sigma$
        is also the limiting distribution of the ergodic chain. For an
        ergodic matrix, the left eigenvector with the largest modulus
        is real and is proportional to the steady state vector.



        eigen(t(P))$vectors     # transpose to get LEFT eigenvectors
        [,1] [,2] [,3]
        [1,] -0.6666667+0i -0.3535534+0.3535534i -0.3535534-0.3535534i
        [2,] -0.3333333+0i -0.3535534-0.3535534i -0.3535534+0.3535534i
        [3,] -0.6666667+0i 0.7071068+0.0000000i 0.7071068+0.0000000i

        s = as.numeric(eigen(t(P))$vectors[,1]); s = s/sum(s); s
        [1] 0.4 0.2 0.4 # first-listed vector has largest modulus

        s %*% P # to verify stationarity
        [,1] [,2] [,3]
        [1,] 0.4 0.2 0.4


        So $sigma = (.4, .2, .4)$ is the limiting distribution.



        Perhaps there is more-elegant R code for this. If so, suggestions are
        welcome.






        share|cite|improve this answer











        $endgroup$



        Comment: Here are some computations in R that I have sometimes
        found convenient for use with ergodic Markov Chains having small finite
        state spaces.
        [If the matrix $mathbf{P}$ is based on empirical data, make sure each row of the
        transition matrix sums exactly to $0.]$



        Establish ergodicity. $mathbf{P}^8$ is a power of the transition matrix in the current Question that
        has all positive elements, so the chain is ergodic.



        P = matrix(c(0, 0, 1,
        1, 0, 0,
        .5,.5, 0), nrow=3, byrow=T)
        P
        [,1] [,2] [,3]
        [1,] 0.0 0.0 1
        [2,] 1.0 0.0 0
        [3,] 0.5 0.5 0

        P2 = P %*% P; P4 = P2 %*% P2; P8 = P4 %*% P4; P8
        [,1] [,2] [,3]
        [1,] 0.4375 0.1875 0.3750
        [2,] 0.3750 0.2500 0.3750
        [3,] 0.3750 0.1875 0.4375


        Compute limiting distribution. The stationary vector $sigma$ with $sigmamathbf{P} = sigma$
        is also the limiting distribution of the ergodic chain. For an
        ergodic matrix, the left eigenvector with the largest modulus
        is real and is proportional to the steady state vector.



        eigen(t(P))$vectors     # transpose to get LEFT eigenvectors
        [,1] [,2] [,3]
        [1,] -0.6666667+0i -0.3535534+0.3535534i -0.3535534-0.3535534i
        [2,] -0.3333333+0i -0.3535534-0.3535534i -0.3535534+0.3535534i
        [3,] -0.6666667+0i 0.7071068+0.0000000i 0.7071068+0.0000000i

        s = as.numeric(eigen(t(P))$vectors[,1]); s = s/sum(s); s
        [1] 0.4 0.2 0.4 # first-listed vector has largest modulus

        s %*% P # to verify stationarity
        [,1] [,2] [,3]
        [1,] 0.4 0.2 0.4


        So $sigma = (.4, .2, .4)$ is the limiting distribution.



        Perhaps there is more-elegant R code for this. If so, suggestions are
        welcome.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Dec 8 '18 at 8:36

























        answered Dec 8 '18 at 8:30









        BruceETBruceET

        35.3k71440




        35.3k71440






























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